Prismatic sealed secondary battery

ABSTRACT

In a prismatic sealed secondary battery according to an embodiment of the present invention, at least one of positive electrode substrate exposed portions and negative electrode substrate exposed portions of an electrode assembly is split into two groups, and therebetween are disposed intermediate members that are made of a resin material and hold one or more connecting conductive members. The two split substrate exposed portions are electrically connected to collector members and to at least one of the connecting conductive members by resistance-welding. Voids are formed in resin material portions of the intermediate members that are located around the resistance-welded portions of the connecting conductive members. Therefore, lowered resistance between the substrate exposed portions and the collector members and stabilized quality of the welds are realized and the manufacturing yield of the prismatic sealed secondary battery is improved.

TECHNICAL FIELD

The present invention relates to a prismatic sealed secondary batterythat has stacked positive electrode substrate exposed portions andnegative electrode substrate exposed portions, in which at least one ofthose sets of substrate exposed portions is split into two groups,connecting conductive members are positioned and disposed between suchtwo groups, and the substrate exposed portions are resistance-welded tocollector members and to the connecting conductive members, so thatlowered resistance and stabilized quality of the welds are realized andthe manufacturing yield is improved.

BACKGROUND ART

With the rise of the environmental protection movement over recentyears, restrictions on emissions of carbon dioxide and other exhaustgases that cause warming have been strengthened. Consequently, theautomobile industry is engaging actively in development of electricvehicles (EVs), hybrid electric vehicles (HEVs) and the like, to replacevehicles that use fossil fuels such as gasoline, diesel oil and naturalgas. As the batteries for such EVs and HEVs, nickel-hydrogen secondarybatteries or lithium ion secondary batteries are used. In recent years,nonaqueous electrolyte secondary batteries such as lithium ion secondarybatteries have come to be used in large numbers for this purpose,because they provide a battery that is both lightweight and highcapacity.

EVs and HEVs are now required not only to be environment-friendly, butalso to have basic performance as vehicles, that is, accelerationperformance, gradient-climbing performance, and other high-level drivingcapabilities. In order to satisfy such requirements, batteries areneeded that have not simply an enhanced battery capacity but also highoutput. The secondary batteries widely used for EVs and HEVs usually areprismatic sealed secondary batteries in which a generation element ishoused inside a prismatic outer can, and the internal resistance of suchbatteries must be reduced to the extent possible, because large currentflows in them when high-output discharge is performed. For this reason,various improvements have been undertaken concerning lowering theinternal resistance by preventing welding faults between the electrodeplate substrates and the collector members in the generation element ofthe battery.

There exist the methods of mechanical caulking, welding, and so forth,for electrically joining the electrode plate substrates and thecollector members so as to effect electrical collection in thegeneration element. For electrical collection in batteries that arerequired to have high output, welding is the appropriate method, sinceit is likely to realize lower resistance and unlikely to deteriorateover time. In lithium ion secondary batteries, aluminum or aluminumalloy is used as the material for the positive electrode platesubstrates and collector members, and copper or copper alloy as thematerial for the negative electrode plate substrates and collectormembers to realize lower resistance. However, aluminum, aluminum alloy,copper, and copper alloy have the characteristics of low electricalresistance and high thermal conductivity, so that an extremely largeamount of energy is required in order to weld them.

The following methods have long been known as methods for weldingtogether the electrode plate substrates and collector members thatconstitute the generation element:

1) Laser welding2) Ultrasonic welding3) Resistance welding

As regards the laser welding method, aluminum, aluminum alloy, copper,and copper alloy, which are the materials to be welded, have a highreflectivity of around 90% with respect to the YAG(yttrium-aluminum-garnet) laser beams that are widely used for metalwelding, and therefore will require a high-energy laser beam.Additionally, with laser welding of aluminum, aluminum alloy, copper, orcopper alloy, there exist the problems that the weldability variesgreatly depending on the influence of the surface condition, and that,as with laser welding of other materials, the occurrence of spatter isunavoidable.

With ultrasonic welding, a large energy is required because of the highthermal conductivity of aluminum, aluminum alloy, copper, and copperalloy, which are the materials to be welded, and there is also the issuethat the positive electrode active material and negative electrodeactive material are prone to fall out due to the ultrasonic vibrationduring the welding.

With resistance welding, furthermore, there are the issues that a largecurrent has to be input in a short time because of the low electricalresistance and high thermal conductivity of aluminum, aluminum alloy,copper, and copper alloy, which are the materials to be welded; thatthere is risk of the resistance welding electrode rods becomingfusion-welded to the collector members during the resistance welding,and that melting or sparks can occur in places other than the weldportions.

The three welding methods each have their merits and drawbacks asdescribed above. However, in the interest of productivity and economy,it is preferable to employ resistance welding, which has long beenwidely used as a method for welding between metals. However, theelectrode assemblies in the lithium ion secondary batteries or otherprismatic sealed secondary batteries used in EVs and HEVs have astructure in which positive electrode plates and negative electrodeplates are stacked or wound with separators interposed therebetween.Furthermore, the substrate exposed portions of the positive electrodeplates and negative electrode plates are disposed so as to be located ondiffering sides to each other, with the stacked positive electrode platesubstrate exposed portions being welded to the positive electrodecollector member, and likewise with the stacked negative electrode platesubstrate exposed portions being welded to the negative electrodecollector member. Where the capacity of a lithium ion secondary batteryor other prismatic sealed secondary battery used for an EV or HEV islarge, the number of these stacked positive electrode plate substrateexposed portions and negative electrode plate substrate exposed portionswill be extremely large.

JP-A-2003-249423 discloses the invention of a storage element having anelectrode assembly formed of positive electrode plates and negativeelectrode plates wound into a flattened shape with separators interposedtherebetween, in which the substrate exposed portions of each electrodeare divided into two bundles for welding to the collector member, inorder to render small the stacking width of the respective electrodesubstrate exposed portions that project out from the separators. Thestructure of the storage element disclosed in JP-A-2003-249423 will nowbe described using FIGS. 9 and 10. FIG. 9A is a cross-sectional view ofan electrical double layer capacitor that serves as the storage elementdisclosed in JP-A-2003-249423, FIG. 9B is a cross-sectional view alongline IXB-IXB in FIG. 9A, FIG. 9C is a cross-sectional view along lineIXC-IXC in FIG. 9A, and FIG. 10 is a view showing the welding processbetween the electrode substrate exposed portions and collector member inFIGS. 9A to 9C.

As FIGS. 9A to 9C show, the storage element 50 has a wound electrodeassembly 51 in which positive electrode plates, negative electrodeplates and interposed separators (all of which are not shown in thefigures) are stacked and wound in a flattened shape, and this woundelectrode assembly 51 is disposed inside a prismatic outer can 52 madeof aluminum. The positive electrode collector member 53 a and negativeelectrode collector member 53 b of the storage element 50 have aU-shaped wing portion 54 a or 54 b, respectively, formed at one end andconnected to the substrate exposed portions 55 a of the positiveelectrode plates or the substrate exposed portions 55 b of the negativeelectrode plates, respectively, with the other end being connected tothe positive electrode terminal 56 a or negative electrode terminal 56b, respectively. Furthermore, the substrate exposed portions 55 a of thepositive electrode plates are divided into two bundles, of which one iswelded to one outer side face of the U-shaped wing portion 54 a and theother to the other outer side face, and likewise, the substrate exposedportions 55 b of the negative electrode plates are divided into twobundles, one of which is welded to one outer side face of the otherU-shaped wing portion 54 b and the other to the other outer side face.

For the positive electrode, for example, ultrasonic welding is performedas follows, as shown in FIG. 10. One of the two split bundles ofsubstrate exposed portions 55 a of the positive electrode plates isdisposed on an outer face of the U-shaped wing portion 54 a, the horn 57of an ultrasonic welding device (not shown in the figure) is broughtinto contact with the outer surface of the substrate exposed portions 55a, and the anvil 58 is disposed on the inner surface of the U-shapedwing portion 54 a. Note that the other bundle of the substrate exposedportions 55 a of the positive electrode plates is ultrasonically weldedwith the same method, and likewise with the negative electrode.

In the case where the two split bundles of positive electrode plates ornegative electrode plates are resistance welded, one will considereither the method of welding each bundle separately or the method ofseries spot welding the bundles simultaneously. Of these, the seriesspot welding method will be preferable in view of the smaller number ofweldings. With the long-used series spot welding technique, in the casewhere, as shown in FIG. 11, the members to be welded 73 and 74 arewelded at two spots coaxially with a pair of resistance weldingelectrode rods 71 and 72, the method that has mainly been used is tointerpose a U-shaped welding piece 75 in the intermediate space andperform the weldings at the top and bottom of the U-shaped welding piece75. This method is in wide general use because the U-shaped weldingpiece 75 can be fabricated with ease from flat sheet metal and becauseit is easy to fabricate projections that will render the resistancewelding both easy and stable.

The invention disclosed in JP-A-2003-249423 yields the advantage thatthe width of the positive electrode exposed portions and of the negativeelectrode exposed portions can be rendered small, and therefore thevolumetric efficiency of the storage device will be good. However, withthis invention, there exist problematic aspects that will render themanufacturing equipment complex. These include the fact that severalweldings are required in order to weld the positive electrode plates andthe negative electrode plates to the positive electrode collector memberand negative electrode collector member, respectively; and furthermore,that an open space is needed in the central portion of the woundelectrode assembly in order for disposition of the welding-purposeU-shaped wing portions of the positive electrode collector member andnegative electrode collector member, and that it is necessary to disposean anvil in the interior of the U-shaped wing portions during theultrasonic welding.

In addition, although it is stated in JP-A-2003-249423 that theultrasonic welding method will preferably be used for the process ofwelding the electrode plates, the number of winding turns in theembodiments is 16 (8 for each of the two split bundles), and the stackthickness is 320 μm. As opposed to this, in large-capacity sealedbatteries such as the lithium ion secondary batteries for EVs and HEVs,the number of stacked positive electrode substrate exposed portions andnegative electrode substrate exposed portions is much greater than inthe case of the invention disclosed in JP-A-2003-249423, and moreoverthe stack thickness is far larger.

Therefore, with large-capacity prismatic sealed batteries such as thelithium ion secondary batteries for EVs and HEVs, in order to use theultrasonic welding method to weld in a stable condition the stackedpositive electrode substrate exposed portions and negative electrodesubstrate exposed portions to the collector members, a large applicationof pressure is required to fit the stacked positive electrode substrateexposed portions and negative electrode substrate exposed portionstightly against their respective collector members, and a large energyis required to make the ultrasonic vibration reach as far as the otherends of the stacked positive electrode substrate exposed portions andnegative electrode substrate exposed portions. With the inventiondisclosed in JP-A-2003-249423, the pressure application and ultrasonicenergy have to be sustained by the anvil disposed in the interior of theU-shaped collector members, which means that the anvil must haveconsiderable rigidity, and in addition it is extremely difficult intechnical terms to find stable welding conditions under which an anvilof the size that can be provided in the collector member interior willsustain the large pressure application.

Furthermore, with the long-used method shown in FIG. 11, the positiveelectrode substrate exposed portions and negative electrode substrateexposed portions can each be series-welded with a single welding, butmeasures such as providing a pressure receiving piece 76 in the interiorof the U-shaped welding piece 75 and a metal block for power conductionare needed in order to eliminate distortion of the U-shaped weldingpiece 75 due to pressure application by the welding electrode rods 71and 72, and such complexification of the welding equipment has been anissue.

In JP-UM-A-58-113268 there is disclosed an electrode plate substrateyoke 80, shown in FIG. 12, in which electrode substrate groups 84 a and84 b, formed by splitting into two bundled groups the substrates 84 ofan electrode assembly 83, are placed against the side faces of the baseportion 82 of a collector member 81 and integrally series spot-weldedthereto together with a pair of stiffening plates 85 a and 85 b disposedon the outer sides of the electrode substrate groups 84 a and 84 b.

JP-A-2000-40501 discloses a flat wound electrode battery 90 that, asshown in FIGS. 13A and 13B, has a flattened wound electrode assembly 93with positive electrode plates and negative electrode plates wound insuch a manner, with separators interposed therebetween, that positiveelectrode substrate exposed portions 91 and negative electrode substrateexposed portions 92 are disposed on opposing sides; and in which, usingfor example a positive electrode terminal 94 consisting of a rectangularconnecting part 94 a that has edge portions made into curved surfacesand that fits into the central hollow space 91 a around which thepositive electrode substrate exposed portions 91 are wound, a terminalpart 94 b that projects longitudinally in the flattening direction,orthogonal to the winding axis direction, and a short connecting part 94c that connects such two parts, electrical connection is effected byfitting the terminal part 94 b of the positive electrode terminal 94into the central hollow space 91 a around which the positive electrodesubstrate exposed portions 91 are wound (see FIG. 13A), then performingseries spot welding on both sides of the positive electrode substrateexposed portions 91.

However, with the series spot welding methods disclosed inJP-UM-A-58-113268 and JP-A-2000-40501, the substrate exposed portions ofthe positive electrode plates and negative electrode plates are splitinto two groups and series spot welded directly to the two sides of thepositive electrode terminal or negative electrode terminal,respectively, and because such welding surfaces on the positiveelectrode terminal or negative electrode terminal are flat surfaces, ithas been difficult to render high the strength of the weldings betweenthe positive electrode terminal or negative electrode terminal and thesubstrate exposed portions of the positive electrode plates or negativeelectrode plates, respectively, and to render small the variation in theinternal resistance of the welds. In addition; there has been the issuethat the positive electrode terminal and negative electrode terminalmust be substantial bodies, which means that the mass of the positiveelectrode terminal and negative electrode terminal will be large.

Also, in large-capacity prismatic sealed secondary batteries such as thelithium ion secondary batteries for EVs and HEVs, the number of stackedpositive electrode substrate exposed portions and negative electrodesubstrate exposed portions is extremely large, and moreover aluminum oraluminum alloy is used for the positive electrode substrates andpositive electrode collector, and copper or copper alloy for thenegative electrode substrates and negative electrode collector. Sincealuminum, aluminum alloy, copper and copper alloy are materials with lowelectrical resistance and with good thermal conductivity, a largewelding energy is required in order to render high the strength ofresistance welding between the positive electrode substrate exposedportions and positive electrode terminal and between the negativeelectrode substrate exposed portions and negative electrode terminal,and in order to render small the internal resistance of the welds.Moreover, when the welding energy is large during resistance welding,the occurrence of spattered dust will increase, and by migrating intothe interior of the electrode assembly, the dust will cause internalshort-circuits or poor pressure resistance, leading to lowering of themanufacturing yield.

SUMMARY

An advantage of some aspects of the present invention is to provide aprismatic sealed secondary battery in which the stacked substrateexposed portions of the positive electrode or of the negative electrode,or of both, are split into two groups, a connecting conductive member isstably positioned and disposed therebetween, and resistance welding isperformed between the substrate exposed portions and the collectormembers and between the substrate exposed portions and the connectingconductive members, so that enhanced resistance of the welds can berealized, and moreover the quality of the welded parts is stabilized andthe manufacturing yield is improved.

According to an aspect of the invention, a prismatic sealed secondarybattery includes: an electrode assembly that has stacked or woundpositive electrode substrate exposed portions and negative electrodesubstrate exposed portions; a positive electrode collector member thatis electrically joined to the positive electrode substrate exposedportions; a negative electrode collector member that is electricallyjoined to the negative electrode substrate exposed portions; and aprismatic outer can. The positive electrode substrate exposed portionsor the negative electrode substrate exposed portions, or both, are splitinto two groups, and therebetween is disposed an intermediate memberthat is made of a resin material and holds one or more connectingconductive members. The collector member for the substrate exposedportions that are split into two groups is disposed on at least one ofthe outermost faces of the substrate exposed portions that are splitinto two groups, and is electrically joined by a resistance weldingmethod to the substrate exposed portions that are split into two groups,together with the one or more connecting conductive members. Voids areformed in the resin material portions of the intermediate member thatare located around the resistance-welded portions of the connectingconductive members.

With such a prismatic sealed secondary battery of the present aspect,the intermediate member that is made of resin material and holds atleast one connective conducting member is disposed between the two splitgroups of positive electrode substrate exposed portions, or of negativeelectrode substrate exposed portions, or of both. The collector memberfor the substrate exposed portions that are split into two groups isdisposed on at least one of the outermost faces of the substrate exposedportions that are split into two groups and is electrically joined by aresistance welding method to the substrate exposed portions that aresplit into two groups, together with the one or more connectingconductive members of the intermediate member.

Consequently, with the prismatic sealed secondary battery of the presentaspect, the substrate exposed portions that are split into two groupscan be joined to the connecting conductive members and the collectormember in a single operation using the series resistance welding method.In addition, when connecting conductive members are provided inplurality, because the plurality of connecting conductive members areheld by the intermediate member made of resin material, the precision ofthe dimensions among the plurality of connecting conductive members canbe improved, and moreover they can be positioned and disposed betweenthe two split groups of substrate exposed portions in a stable state, sothat the quality of the resistance welds is improved, enabling loweredresistance to be realized. For these reasons, a prismatic sealedsecondary battery with raised output and lessened output variation isobtained with the present aspect of the invention.

Furthermore, with the prismatic sealed secondary battery according tothe present aspect of the invention, voids are formed in the resinmaterial portions of the intermediate member that are located around theresistance-welded portions of the connecting conductive members. Moreprecisely, the resin material portions of the intermediate member aredisposed in such a state as to substantially contact with or beproximate to both of the inner surfaces of the two split groups ofsubstrate exposed portions, and also in such a state that voids areformed in the resin material portions of the intermediate member thatare located around the resistance-welded portions of the connectingconductive members.

Consequently, the spattered dust and melted metal that occur duringresistance welding will immediately be captured inside the voids formedaround the connecting conductive members, and if they collide with theresin material portions of the intermediate member, will be cooled andcaptured on the surfaces or in the interior of such resin materialportions, and therefore will seldom leap out to the exterior of thecollector or be dispersed into the interior of the electrode assembly.Thus, the invention enables a prismatic sealed secondary battery to beobtained that has low occurrence of internal short-circuits and stablequality of welds, as well as high reliability with improvedmanufacturing yield. Note that with the invention, the fact that thespattered dust and melted metal that occur during resistance welding arecaptured also by the rein material portions of the intermediate membermeans that the voids do not necessarily need to be formed as perfectrings; they may be formed discontinuously (with gapped portions in thering) around the resistance-welded portions of the connecting conductivemembers, and as regards their shape, they may take the form of acircular ring, an elliptical ring, or even a rectangular ring, asdesired.

Note that with the prismatic sealed secondary battery of the presentaspect, the intermediate member, which is made of resin material, willbe provided with one or more connecting conductive members, but sincewith one connecting conductive member the intermediate member made ofresin material is prone to move rotationally with the weld point of theconnecting conductive member as pivot point, the intermediate membermade of resin material is preferably provided with a plurality ofconnecting conductive members in order to stabilize disposition of theintermediate member made of resin material and enable large-currentcharge/discharge. Additionally, in the prismatic sealed secondarybattery of the present aspect, an intermediate member made of resinmaterial may be disposed on the positive electrode substrate exposedportions or on the negative electrode substrate exposed portions, or onboth, but will preferably be provided on both.

Note that in the present aspect of the invention, although a collectormember for the two split groups of substrate exposed portions may bedisposed on either or both of the outermost faces of the two splitgroups of substrate exposed portions, it is preferable that a collectormember be disposed on both such outermost faces. However, by disposingon the other of the two outermost faces of the two split groups ofsubstrate exposed portions a collection receiving member that is notdirectly connected to the electrode terminal, a functional effect can beexerted that is substantially the same as the case where a collectormember is disposed on both outermost faces of the two split groups ofsubstrate exposed portions. Hence, the meaning of “collector member” asused herein includes such a “collection receiving member”.

Note further that resistance welding can be executed in a morephysically stable state if a collector member is disposed on both of theoutermost faces of the two split groups of substrate exposed portions.Moreover, it will be possible not to dispose anything on the other ofthe two outermost faces of the two split groups of substrate exposedportions, and to perform the resistance welding by bringing one of thepairs of resistance welding electrodes directly into contact with thatface. However, in that case, there will be a possibility of fusionoccurring between the resistance welding electrodes and the other of thetwo outermost faces of the two split groups of substrate exposedportions. Therefore, it will be preferable either to dispose on each ofthe two outermost faces of the two split groups of substrate exposedportions a collector member that is connected to the electrode terminal,or else to dispose on one of such faces a collector member connected tothe electrode terminal and dispose on the other of such faces acollection receiving member that serves as a collector member.

Examples of the resin material that can be used for the intermediatemember in the prismatic sealed secondary battery of the present aspectinclude polypropylene, polyethylene, polyvinylidene chloride,polyacetal, polyamide, polycarbonate, and polyphenylene sulfide. Thewidth of the resin material portions of the intermediate member may begreater than or smaller than the length of the connecting conductivemembers, provided that such width is determined so that the surfaces(excepting the slot portions) of the resin material portions that areopposed to the substrate exposed portions in the vicinity of theconnecting conductive members will contact with the substrate exposedportions after welding has been performed. However, there will be alarge degree of deformation in the substrate exposed portions if thedifference between the width of the resin material portions of theintermediate member and the length of the connecting conductive membersis large, and so the width of the resin material portions of theintermediate member will preferably be on the order of 0.8 to 1.2 timesthe length of the connecting conductive members.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that the voids be constituted of slots formed between theresin material portions of the intermediate member and the connectingconductive members.

Since resin material is more readily processable than metallic material,and moreover since the voids take the form of slots formed between theresin material portions of the intermediate member and the connectingconductive members, voids of a particular size can be formed with ease.Therefore, this aspect of the invention enables a prismatic sealedsecondary battery that yields the foregoing advantages to bemanufactured with ease.

In the prismatic sealed secondary battery of the present aspect, thevoids may alternatively be constituted of slots formed in the resinmaterial portions in positions distanced from the resistance-weldedportions.

With the prismatic sealed secondary battery of the present aspect, theresin material portions of the intermediate member are disposed in sucha state as to substantially contact with or be proximate to both of theinner surfaces of the two split groups of substrate exposed portions,and so the spattered dust and melted metal that occur during resistancewelding will migrate to the areas around the resistance-welded portionsby passing through the interior of the resin material portions of theintermediate member or between the resin material portions of theintermediate member and the substrate exposed portions. Because of this,with the prismatic sealed secondary battery of the present aspect, themigration resistance of the spattered dust and melted metal that occurduring resistance welding is high, which means that they will readily becaptured inside the resin material portions or inside slots formed inthe resin material portions in positions distanced from theresistance-welded portions.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that the electrode assembly be inserted into the prismaticouter can in such a manner that the positive electrode substrate exposedportions are positioned at one end, and the negative electrode substrateexposed portions at the other end, of the prismatic outer can, and thusthat the resin material portions of the intermediate member protrude, inthe extension direction of the two split groups of substrate exposedportions, beyond the ends of the two split substrate exposed portionsand the ends of the collector member to the prismatic outer can.

With the prismatic sealed secondary battery of the present aspect, theelectrode assembly is inserted into the prismatic outer can in such amanner that the positive electrode substrate exposed portions arepositioned at one end, and the negative electrode substrate exposedportions at the other end, of the prismatic outer can, which means that,with the protruding resin material portions of the intermediate memberpositioned at the two inside ends of the prismatic outer can, the riskof the ends of the two split groups of substrate exposed portions andthe ends of the collector member contacting with the two inside ends ofthe prismatic outer can is eliminated. Hence, such a prismatic sealedsecondary battery of the present aspect will be a highly reliableprismatic sealed secondary battery in which the risk of the positiveelectrode substrate exposed portions or the negative electrode substrateexposed portions short-circuiting with the prismatic outer can issuppressed.

Usually in prismatic sealed secondary batteries, the electrode assemblyis wrapped in a folded-back plate-like resin sheet when inserted intothe prismatic outer can, and with the prismatic sealed secondary batteryof the present aspect, even if the resin sheet is mispositioned,contacting of the positive electrode substrate exposed portions or thenegative electrode substrate exposed portions with the prismatic outercan will be reliably suppressed because the protruding resin materialportions of the intermediate member will be positioned at the two insideends of the prismatic outer can of the electrode assembly. Moreover, ifexternal force should act on the prismatic sealed secondary battery ofthe present aspect and deform the outer can, the possibility of thepositive electrode substrate exposed portions or the negative electrodesubstrate exposed portions contacting with the prismatic outer can willbe smaller than in the case where the electrode assembly is coveredsimply by a resin sheet, because the resin material portions of theintermediate member are rigid bodies and therefore are not likely todeform. Thus, a prismatic sealed secondary battery with high reliabilitycan be obtained.

In addition, the resin material portions of the intermediate member areof such a size as to protrude beyond both the ends of the substrateexposed portions and the ends of the collector member when theintermediate member has been inserted between the two split groups ofpositive electrode substrate exposed portions or of negative electrodesubstrate exposed portions, which means that the intermediate member canbe clasped at its protruding resin material portion when it is insertedbetween the two split groups of substrate exposed portions, therebyyielding the additional advantages of facilitating insertion,facilitating the clasping of the intermediate member, and facilitatingassembly.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that flat portions be provided on portions of the resinmaterial portions of the intermediate member that are opposed to theprismatic outer can. In such a case, it is preferable that chamferedportions be formed on the angled portions of the resin material portionsof the intermediate member that are opposed to the prismatic outer can.

With flat portions being provided on those portions of the resinmaterial portions of the intermediate member that are opposed to theprismatic outer can, assembly will be easier, because by placing theflat portions of the resin material portions of the intermediate memberagainst at least one of the two ends of the prismatic outer can duringinsertion of the electrode assembly into the prismatic outer can, theelectrode assembly can be inserted by being slid in. Moreover, withchamfered portions being formed on the angled portions of the resinmaterial portions of the intermediate member that are opposed to theprismatic outer can, insertion into the prismatic outer can will beeasier, and furthermore, even where the electrode assembly is wrapped ina folded-back plate-like resin sheet when inserted into the prismaticouter can, ripping of the resin sheet by the angled portions of theresin material portions of the intermediate member will be suppressed.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that chamfered portions be formed on the angled portions ofthe resin material portions of the intermediate member that are on theside that is inserted into the substrate exposed portions that are splitinto two groups.

With chamfered portions being formed on the angled portions of the resinmaterial portions of the intermediate member that are on the side thatis inserted into the two split groups of substrate exposed portions inthe prismatic sealed secondary battery of the present aspect, duringinsertion of the intermediate member between the stacked substrateexposed portions, the intermediate member, having the chamfered portionsformed in it, will seldom cause damage to the pliable substrate exposedportions if it contacts them, and the connecting conductive members caneasily be made to contact against the substrate exposed portions. As aresult, the weldability will be improved.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that the resin material portions of the intermediate memberare provided with a gas venting hole or cutout, or both.

If the intermediate member is provided with gas venting holes orcutouts, any gas that may be generated in the electrode assemblyinterior in the event that abnormality occurs in the battery can easilybe expelled to the exterior of the electrode assembly, and since thepressure-sensitive type current interruption mechanism, gas exhaustvalve, and so forth, with which a prismatic sealed secondary battery isnormally equipped will be activated stably, safety can be secured. Inaddition, the volume of the intermediate member will be reduced, andtherefore it will be possible to render the prismatic sealed secondarybattery lighter.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that the connecting conductive members are block-shaped orcolumnar body-shaped.

With the connecting conductive members being block-shaped or columnarbody-shaped in the prismatic sealed secondary battery of the presentaspect, deformation will be unlikely to occur when the pushing pressureis applied during resistance welding, the physical properties of thewelds will be stabilized, and moreover the quality of the welds will begood. Note that shapes that are not liable to deformation, such ascircular columnar, square columnar, elliptical columnar, circularcylindrical, square cylindrical, or elliptical cylindrical, can beemployed for the shape of the connecting conductive members.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that the angled portions of two mutually opposed surfaces ofthe block shapes or columnar body shapes have chamfered portions.

With the angled portions of two mutually opposed surfaces of the blockshapes or columnar body shapes having chamfered portions in theprismatic sealed secondary battery of the present aspect, duringinsertion of the intermediate member between the stacked substrateexposed portions, the connecting conductive members will cause littledamage to the pliable substrate exposed portions if they contact them,and the connecting conductive members can easily be made to contactagainst the substrate exposed portions. As a result, the weldabilitywill be improved. Moreover, since the areas of the two opposed surfacesof the connecting conductive members become small, those surfaces willact as projections, which means that the current will be concentratedand heat-up will readily take place, so that the physical properties ofthe welds will be stabilized, and moreover the quality of the welds willbe good.

In the prismatic sealed secondary battery of the present aspect, it ispreferable that the surfaces provided with the chamfered portions of theconnecting conductive members be planes.

The surfaces provided with the chamfered portions of the connectingconductive members can take the form either of curved surfaces or ofplanes. However, if the surfaces provided with the chamfered surfacestake the form of planes, then during insertion of the intermediatemember between the stacked substrate exposed portions, the surfaces withchamfered angled portions and the surfaces of the intermediate memberwhere the connecting conductive members are exposed will, of necessity,form obtuse angles with respect to the substrate exposed portions. Forthis reason, the substrate exposed portions and the connectingconductive members will readily come into contact when the intermediatemember is inserted between the stacked substrate exposed portions andresistance welding is performed in the prismatic sealed secondarybattery of the present aspect. As a result, the weldability will beimproved.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein the same numbers refer to the same elementsthroughout.

FIG. 1A is a cross-sectional view of a prismatic nonaqueous electrolytesecondary battery of a First Embodiment of the invention, FIG. 1B is across-sectional view along line IB-IB in FIG. 1A, FIG. 1C is across-sectional view along line IC-IC in FIG. 1A, and FIG. 1D is anenlarged view of the portion ID in FIG. 1C.

FIG. 2A is a top view of a positive electrode connecting conductivemember in the First Embodiment, FIG. 2B is a cross-sectional view alongline IIB-IIB in FIG. 2A, FIG. 2C is a front view of the positiveelectrode connecting conductive member, FIG. 2D is a cross-sectionalview of a positive electrode intermediate member, FIG. 2E is across-sectional view along line IIE-IIE in FIG. 2D, FIG. 2F is a topview of a variation in which a chamfered position in the positiveelectrode intermediate member is altered, and FIG. 2G is a top viewshowing the state in which the positive electrode intermediate member inFIG. 2F is mounted on an electrode assembly.

FIG. 3A is a cross-sectional view showing the welding conditionspertaining to the First Embodiment, and FIG. 3B is an enlarged view ofthe portion IIIB in FIG. 3A, illustrating the conditions of theresistance welding being finished.

FIG. 4A is a view showing the route by which the resistance weldingcurrent flows in the case where the portion of the protrusion thatcontacts with the positive electrode substrate exposed portions isannular, FIG. 4B is a view showing the portions in FIG. 4A where heat-upis intense, FIG. 4C is a view showing the route by which the resistancewelding current flows in the case where the portion of the protrusionthat contacts with the positive electrode substrate exposed portions iscircular, and FIG. 4D is a view showing the portions in FIG. 4C whereheat-up is intense.

FIGS. 5A to 5C are schematic views showing the shape of the positiveelectrode connecting conductive member pertaining to Second to FourthEmbodiments, respectively, of the invention, and FIG. 5D is a schematicside view showing the positive electrode intermediate member of theFourth Embodiment in the state where it has been installed to thepositive electrode substrate exposed portions, which are split into twogroups.

FIG. 6A is a side view showing the post-welding disposition of thepositive electrode connecting conductive member portion pertaining to aFifth Embodiment of the invention, and FIG. 6B is a side view showingthe post-welding disposition of the positive electrode connectingconductive member portion pertaining to a Sixth Embodiment of theinvention.

FIGS. 7A to 7C are front views showing the shape of the positiveelectrode intermediate member in Seventh to Ninth Embodiments,respectively, of the invention.

FIG. 8A is a longitudinal sectional view of a positive electrodeintermediate member 24 ₄ pertaining to a Tenth Embodiment, FIG. 8B is alongitudinal sectional view of a positive electrode intermediate member24 ₅ pertaining to an Eleventh Embodiment, and FIG. 8C is a longitudinalsectional view of a positive electrode intermediate member 24 ₆pertaining to a Twelfth Embodiment.

FIG. 9A is a cross-sectional view of an electrical double layercapacitor which serves as a storage element in the related art, FIG. 9Bis a cross-sectional view along line IXB-IXB in FIG. 9A, and FIG. 9C isa cross-sectional view along line IXC-IXC in FIG. 9A.

FIG. 10 is a view showing the welding process between an electrodesubstrate exposed portion and collector member in FIGS. 9A to 9C.

FIG. 11 is a view explicating the series spot welding method that haslong been in use.

FIG. 12 is a cross-sectional view of an electrode plate substrate yokethat has been welded with the series spot welding method that has longbeen in use.

FIG. 13A is an exploded perspective view of a positive electrodeterminal and positive electrode substrate exposed portions in thepre-welding state in another example of the related art, and FIG. 13B isa perspective view of those items in the post-welding state.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Preferred embodiments for carrying out the invention will now bedescribed in detail with reference to the accompanying drawings.However, it should be remembered that the various embodiments set forthbelow are intended by way of examples for understanding the technicalconcepts of the invention, and not by way of limiting the invention tothese particular prismatic sealed secondary batteries. The invention canequally well be applied to produce many different variants of theembodiments without departing from the scope and spirit of the technicalconcepts set forth in the claims. Note that although the invention isapplicable to a flattened battery that uses a generation element, aplurality of positive electrode substrate exposed portions formed at oneend and a plurality of negative electrode substrate exposed portionsformed at the other end, which can be made either by stacking or bywinding positive electrode plates and negative electrode plates withseparators interposed therebetween, the embodiment descriptions belowuse flattened wound electrode assemblies as representative examples.

First Embodiment

First of all, as an example of a prismatic sealed secondary battery of aFirst Embodiment of the invention, a prismatic nonaqueous electrolytesecondary battery will be described using FIGS. 1 to 3. FIG. 1A is across-sectional view of a prismatic nonaqueous electrolyte secondarybattery of the First Embodiment, FIG. 1B is a cross-sectional view alongline IB-IB in FIG. 1A, FIG. 1C is a cross-sectional view along lineIC-IC in FIG. 1A, and FIG. 1D is an enlarged view of the portion ID inFIG. 1C. FIG. 2A is a top view of a positive electrode connectingconductive member in the First Embodiment, FIG. 2B is a cross-sectionalview along line IIB-IIB in FIG. 2A, FIG. 2C is a front view of thepositive electrode connecting conductive member, FIG. 2D is across-sectional view of a positive electrode intermediate member, FIG.2E is a cross-sectional view along line IIE-IIE in FIG. 2D, FIG. 2F is atop view of a modification in which a chamfered position in the positiveelectrode intermediate member is modified, and FIG. 2G is a top viewshowing a state in which the positive electrode intermediate member inFIG. 2F is mounted on an electrode assembly. FIG. 3A is a side viewshowing the welding conditions pertaining to the First Embodiment, andFIG. 3B is an enlarged view of the portion IIIB in FIG. 3A, illustratingthe conditions of the resistance welding being finished.

This prismatic nonaqueous electrolyte secondary battery 10 has aflattened wound electrode assembly 11 in which positive electrode platesand negative electrode plates are wound with separators interposedtherebetween (all of these are not shown in the figures). The positiveelectrode plates are fabricated by spreading positive electrode activematerial mixture over both faces of a positive electrode substrateconstituted of aluminum foil, drying such mixture and rolling theresulting plate, then slitting the plate so that a strip of aluminumfoil is exposed. Likewise, the negative electrode plates are fabricatedby spreading negative electrode active material mixture over both facesof a negative electrode substrate constituted of copper foil, dryingsuch mixture and rolling the resulting plate, then slitting the plate sothat a strip of copper foil is exposed.

Next, the positive electrode plates and negative electrode plates thusobtained are displaced so that the aluminum foil exposed portions of thepositive electrode plates do not overlie the active material layer ofone of the opposed electrodes, and the copper foil exposed portions ofthe negative electrode plates do not overlie the active material layerof the other opposed electrode, and are then wound with polyethyleneporous separators interposed therebetween, to produce a flattened woundelectrode assembly 11 that has a plurality of positive electrodesubstrate exposed portions 14 piled one above another at one end in thewinding axis direction, and a plurality of negative electrode substrateexposed portions 15 piled one above the other at the other end.

The plurality of positive electrode substrate exposed portions 14 arestacked and connected via positive electrode collector members 16 to apositive electrode terminal 17, and likewise the plurality of negativeelectrode substrate exposed portions 15 are stacked and connected vianegative electrode collector members 18 to a negative electrode terminal19. Note that the positive electrode terminal 17 and the negativeelectrode terminal 19 are each fixed to a sealing plate 13 with aninsulating member 20, 21 respectively, interposed. To fabricate thisprismatic nonaqueous electrolyte secondary battery 10 of the FirstEmbodiment, the flattened wound electrode assembly 11 fabricated in theforegoing manner is inserted, with an insulating resin sheet 23interposed all around except for the sealing plate 13 edge, into aprismatic outer can 12, after which the sealing plate 13 is laser-weldedto the mouth portion of the outer can 12, then nonaqueous electrolyte ispoured in through an electrolyte pour hole 22, and the electrolyte pourhole 22 is sealed over.

In the positive electrode part of the flattened wound electrode assembly11, as shown in FIGS. 1B and 1C, the stacked plurality of positiveelectrode substrate exposed portions 14 are split into two groups,between which is sandwiched a positive electrode intermediate member 24that is constituted of resin material and holds one or more (two in thisexample) positive electrode connecting conductive members 24A. Likewisein the negative electrode part, the stacked plurality of negativeelectrode substrate exposed portions 15 are split into two groups,between which is sandwiched a negative electrode intermediate member 25that is constituted of resin material and holds two negative electrodeconnecting conductive members 25A. Also, on each of the two outermostsurfaces of the positive electrode substrate exposed portions 14,located at the two sides of the positive electrode connecting conductivemembers 24A, there is disposed a positive electrode collector member 16,and on each of the two outermost surfaces of the negative electrodesubstrate exposed portions 15, located at the two sides of the negativeelectrode connecting conductive members 25A, there is disposed anegative electrode collector member 18. Specific structures and featuresof the positive electrode intermediate member 24, the negative electrodeintermediate member 25, the positive electrode connecting conductivemembers 24A, and the negative electrode connecting conductive members25A will be described in greater detail later.

Note that the positive electrode connecting conductive members 24A aremade of the same material, namely, aluminum, as the positive electrodesubstrates, and the negative electrode connecting conductive members 25Aare made of the same material, namely, copper, as the negative electrodesubstrates, but the shapes of the positive electrode connectingconductive members 24A and the negative electrode connecting conductivemembers 25A may either be the same or differ. Examples of the resinmaterial that can be used for the positive electrode intermediate member24 and the negative electrode intermediate member 25 includepolypropylene (PP), polyethylene (PE), polyvinylidene chloride (PVDC),polyacetal (POM), polyamide (PA), polycarbonate (PC), and polyphenylenesulfide (PPS).

Note that in the prismatic nonaqueous electrolyte secondary battery 10of the First Embodiment, as FIGS. 1A, 1B and 2D show, the positiveelectrode intermediate member 24 and the negative electrode intermediatemember 25 hold two positive electrode connecting conductive members 24Aor negative electrode connecting conductive members 25A, respectively,as an example, but the number of positive electrode connectingconductive members 24A or negative electrode connecting conductivemembers 25A that is provided may alternatively, depending on the batteryoutput, for example, that is required, be one, or be three or more. Inparticular, when a plurality of connecting conductive members areprovided in an intermediate member, the fact that all of the connectingconductive members are held by one intermediate member that is made ofresin material will mean that the precision of the dimensions among theconnecting conductive members can be improved, and moreover that theycan be positioned and disposed between the two split groups of substrateexposed portions in a stable state

Resistance welding is performed both between these positive electrodecollector members 16 and the positive electrode substrate exposedportions 14, and between the positive electrode substrate exposedportions 14 and the positive electrode connecting conductive members 24A(at four places in each case, see FIG. 1B). Likewise, connection iseffected, by resistance welding, between the negative electrodecollector members 18 and the negative electrode substrate exposedportions 15, and between the negative electrode substrate exposedportions 15 and the negative electrode connecting conductive members 25A(at four places in each case).

Detailed descriptions will now be given, using FIGS. 2 and 3, of thespecific manufacturing method for the flattened wound electrode assembly11, together with the resistance welding method using the positiveelectrode substrate exposed portions 14, the positive electrodecollector members 16 and the positive electrode intermediate member 24having positive electrode connecting conductive members 24A, and of theresistance welding method using the negative electrode substrate exposedportions 15, the negative electrode collector members 18 and thenegative electrode intermediate member 25 having negative electrodeconnecting conductive members 25A. Since, however, the shapes of thepositive electrode connecting conductive members 24A and positiveelectrode intermediate member 24 can be substantially identical withthose of the negative electrode connecting conductive members 25A andnegative electrode intermediate member 25, and moreover since theresistance welding methods in both cases are substantially similar, thedescriptions below use the positive electrode plate items asrepresentative examples.

First of all, the positive electrode substrate exposed portions 14 ofthe flattened wound electrode assembly 11, which had been obtained bydisplacing the positive electrode plates and negative electrode platesso that the aluminum foil exposed portions of the positive electrodeplates did not overlie the active material layer of one of the opposedelectrodes, and the copper foil exposed portions of the negativeelectrode plates did not overlie the active material layer of the otheropposed electrode, then winding the electrode plates with polyethyleneporous separators interposed therebetween, were split into two groups,one on either side from the central portion of the winding, and eachgroup of positive electrode substrate exposed portions 14 was bundledcentered on ¼ of the electrode assembly thickness. The thickness of thealuminum foil bundle in each group is approximately 660 μm, and thetotal number of stacked foils is 88 (44 in each group). The positiveelectrode collector members 16 are fabricated by punching andbend-processing, etc., an 0.8-mm thick aluminum sheet. Note that thepositive electrode collector members 16 may alternatively be fabricatedby casting, etc., from aluminum sheet.

Then the positive electrode collector members 16 and the positiveelectrode intermediate member 24 having positive electrode connectingconductive members 24A are inserted between the two split groups ofpositive electrode substrate exposed portions 14, with the positiveelectrode collector members 16 being inserted onto the two outermostsurfaces of the positive electrode substrate exposed portions 14 and thepositive electrode intermediate member 24 being inserted into the innerperiphery thereof, in such a manner that the truncated cone shapedprotrusions 24 b of the positive electrode intermediate member 24 eachcontact against the positive electrode substrate exposed portions 14.

There follows an explication, using FIGS. 2A to 2C, of the shape of thepositive electrode connecting conductive members 24A held by thepositive electrode intermediate member 24 in the First Embodiment. Inthese positive electrode connecting conductive members 24A, a protrusion24 b with, e.g., a truncated cone shape is formed on each of two opposedfaces 24 e of the circular columnar main body 24 a. In the centralportion of this truncated cone-shaped protrusion 24 b there is formed anaperture 24 c extending from the tip into the interior of the circularcolumnar main body 24 a. Angled portions 24 f are formed between the twoopposed faces 24 e and the side surfaces 24 h of the circular columnarmain body 24 a.

It is desirable that the height H1 of the truncated cone-shapedprotrusion 24 b be comparable with that of protrusions (projections)that are ordinarily formed on resistance welding members, that is,several mm or so. As regards the depth D of the aperture 24 c, which inthe present example is larger than the height H1 of the truncatedcone-shaped protrusion 24 b, the aperture 24 c will preferably be formedfrom the face 24 e, where the protrusion 24 b is formed, of the circularcolumnar main body 24 a, as far as a position located inward to adistance less than the height H1 of the protrusion 24 b (with the depthD of the aperture 24 c being less than 2H1), or more preferably, as faras a position located inward to a distance less than ½ of the height H1of the protrusion 24 b from the surface of the circular columnar mainbody 24 a where the protrusion 24 b is provided (with the depth D of theaperture 24 c being less than 3/2 H1).

It is desirable that the diameter and length of the circular columnarmain body 24 a be on the order of three mm to several tens of mm, thoughthese dimensions will vary with the flattened wound electrode assembly11, outer can 12, and other parts (see FIGS. 1A to 1D). Note thatalthough the shape of the main body 24 a of the positive electrodeconnecting conductive members 24A is described here as circularcolumnar, any desired shape that has the form of a metallic block, suchas square columnar or elliptical columnar can be used. Also, as thematerial for forming the positive electrode connecting conductivemembers 24A, copper, copper alloy, aluminum, aluminum alloy, tungsten,molybdenum, or the like, can be used. Furthermore, variants of suchitems constituted of such metals can be used, by for example applyingnickel plating to the protrusion 24 b, or changing the material of theprotrusion 24 b and its base area to tungsten or molybdenum, whichpromotes the emission of heat, and joining it by brazing, for example,to the main body 24 a of the positive electrode connecting conductivemembers 24A constituted of copper, copper alloy, aluminum, or aluminumalloy.

Note that in the First Embodiment, there are two positive electrodeconnecting conductive members 24A, which are held integrally by thepositive electrode intermediate member 24 that is made of resinmaterial. In such a case, the plurality of positive electrode connectingconductive members 24A are held in such a manner as all to be parallelto each other. The shape of the positive electrode intermediate member24 can take any square columnar, elliptical columnar, or like form, thatis desired, but is configured to have a horizontally long squarecolumnar form in order to be stably positioned and fixed in the positiveelectrode substrate exposed portions 14 split into two groups.

The length w of the square columnar positive electrode intermediatemember 24 will vary with the size of the prismatic nonaqueouselectrolyte secondary battery, but can be on the order of 20 mm toseveral tens of mm. The width h may be greater than or smaller than thedistance H2 between the two ends of the positive electrode connectingconductive member 24A, provided that such width h is determined so thatthe surfaces (excepting the slot portions) of the resin material portion24 p that are opposed to the positive electrode substrate exposedportions 14 in the vicinity of the positive electrode connectingconductive member 24A will contact with the positive electrode substrateexposed portions 14 after welding has been performed. However, therewill be a large degree of deformation in the positive electrodesubstrate exposed portions 14 if the difference between the width h ofthe resin material portion 24 p of the intermediate member 24 and thedistance H2 between the two ends of the positive electrode connectingconductive member 24A is large, and so the width h of the resin materialportion 24 p of the positive electrode intermediate member 24 willpreferably be on the order of 0.8 to 1.2 times the distance H2 betweenthe two ends of the positive electrode connecting conductive member 24A.

In the case where the shape of the connecting conductive members is,like the positive electrode intermediate member 24, that of a circularcolumnar main body part, on two opposed faces of which are providedprotrusions of, say, a truncated cone shape, it is preferable that theheight H3 of the main body part be smaller than the width h of the resinmaterial portion, and either that the height H2 of the connectingconductive member be the same as the width h of the resin materialportion or that the tip of the protrusion protrude from the resinmaterial portion so that H2≧h.

In the positive electrode intermediate member 24 of the FirstEmbodiment, a flat-bottomed slot 24 q is formed, in a ring-form, in theresin material portion 24 p located around the positive electrodeconnecting conductive member 24A. Note that this ring-form slot 24 q maybe of any depth and width, but in the present example the ring-form slot24 q is provided in such a manner that parts of the surfaces 24 e at thetwo ends of the positive electrode connecting conductive member 24A, andthe lateral surfaces 24 h thereof, are exposed. More precisely, in thepositive electrode intermediate member 24 of the First Embodiment, thewidth h of the resin material portion 24 p is made to be such that H2≧hwith respect to the distance H2 between the two ends of the positiveelectrode connecting conductive member 24A, which means that, around thepositive electrode connecting conductive member 24A, the ring-form voids24 r of the invention are formed between the ring-form slots 24 q formedin the resin material portion 24 p of the positive electrodeintermediate member 24, on the one hand, and the surfaces 24 e and 24 hand the protrusion 24 b of the positive electrode connecting conductivemember 24A, on the other. Thus, these ring-form slots 24 q constitute apart of the “voids” of the invention.

As FIG. 1D shows, in the resin material portion 24 p of the positiveelectrode intermediate member 24, there is formed, in the extensiondirection of the two split groups of positive electrode substrateexposed portions 14, a protruding portion 24 t that protrudes beyond theends 14 t of the two split groups of positive electrode substrateexposed portions 14 and the ends 16 t of the positive electrodecollector members 16 toward the prismatic outer can 12. With such astructure being employed, the protruding portion 24 t of the resinmaterial portion 24 p of the positive electrode intermediate member 24will be positioned at least one of the ends of the flattened woundelectrode assembly 11, which are positioned at the inside ends of theprismatic outer can 12, and so the risk of the ends 14 t of the twosplit groups of positive electrode substrate exposed portions 14 and theends 16 t of the positive electrode collector members 16 both contactingwith the inside of the prismatic outer can 12 will be eliminated.

Moreover, since the protruding portion 24 t of the resin materialportion 24 p of the positive electrode intermediate member 24 protrudesbeyond the ends 14 t of the substrate exposed portions 14 and the ends16 t of the collector members 16 when inserted between the two splitgroups of positive electrode substrate exposed portions 14, the positiveelectrode intermediate member 24 can be clasped at the protrudingportion 24 t when being inserted between the two split groups ofpositive electrode substrate exposed portions 14, thereby facilitatingthe insertion.

The flattened wound electrode assembly 11 will be usually wrapped in afolded-back plate-like resin sheet 23 when inserted into the prismaticouter can 12, and thanks to the presence of the protruding portion 24 tof the resin material portion 24 p of the positive electrodeintermediate member 24, even if the resin sheet 23 is mispositioned,contacting of the ends 14 t of the positive electrode substrate exposedportions 14 and the ends 16 t of the positive electrode collectormembers 16 with the prismatic outer can 12 will be reliably suppressed.If external force should act on the prismatic nonaqueous electrolytesecondary battery 10 and deform the prismatic outer can 12, thepossibility of the ends 14 t of the positive electrode substrate exposedportions 14 and the ends 16 t of the positive electrode collectormembers 16 contacting with the prismatic outer can 12 will be smallerthan in the case where the electrode assembly 11 is covered simply bythe resin sheet 23, because, unlike the resin sheet 23, the resinmaterial portion 24 p of the positive electrode intermediate member 24is a rigid body and therefore is not likely to deform.

Furthermore, a flat portion 24 u is formed on that portion of theprotruding portion 24 t of the resin material portion 24 p of thepositive electrode intermediate member 24 that is opposed to theprismatic outer can 12, and chamfered portions 24 u′ are formed on thelongitudinal angled portions of the flat portion 24 u. With such astructure provided, assembly will be easier, because by placing the flatportion 24 u of the protruding portion 24 t of the resin materialportion 24 p of the positive electrode intermediate member 24 against atleast one of the ends of the prismatic outer can 12 during insertion ofthe flattened electrode assembly 11 into the prismatic outer can 12, theelectrode assembly 11 can be inserted by being slid in. Moreover, withchamfered portions 24 u′ being formed on the longitudinal angledportions of the flat portion 24 u of the protruding portion 24 t of theresin material portion 24 p of the positive electrode intermediatemember 24, insertion into the prismatic outer can 12 will be easier, andfurthermore, even where the flattened electrode assembly 11 is wrappedin a folded-back plate-like resin sheet 23 when inserted into theprismatic outer can 12, ripping of the resin sheet 23 by the angledportions of the protruding portion 24 t of the resin material portion 24p of the positive electrode intermediate member 24 will be suppressed.

In the resin material portion 24 p of the positive electrodeintermediate member 24 that is used in the First Embodiment, chamferedportions 24 v are formed on the angled portions of the side that isinserted into the two split groups of positive electrode substrateexposed portions 14. With such a structure provided, during insertion ofthe positive electrode intermediate member 24 between the two splitgroups of stacked positive electrode substrate exposed portions 14, thechamfered portions 24 v of the positive electrode intermediate member 24will cause little damage to the positive electrode substrate exposedportions 14 if they contact them, and the positive electrode connectingconductive members 24A can be made to contact against the inner face ofthe split groups of positive electrode substrate exposed portions 14when the positive electrode intermediate member 24 is inserted betweenthe two split groups of positive electrode substrate exposed portions14.

Note that in the foregoing First Embodiment, the chamfered portions 24u′ formed on the longitudinal angled portions of the flat portion 24 uof the protruding portion 24 t of the resin material portion 24 p of thepositive electrode intermediate member 24 are described as an example,but as a variant of that, chamfered portions 24 u″ could be formed onthe widthwise angled portions of the flat portion 24 u on the side ofthe protruding portion 24 t of the resin material portion 24 p of thepositive electrode intermediate member 24 that is opposed to the bottomof the prismatic outer can 12. With such a structure, the state when thepositive electrode intermediate member 24 has been inserted into the twosplit groups of positive electrode substrate exposed portions 14 will bethat shown in FIG. 2G, and so when, after resistance welding, theelectrode assembly 11 with the positive electrode intermediate member 24installed thereto is inserted into the prismatic outer can 12, even ifwrapped in a folded-back plate-like resin sheet 23, the electrodeassembly 11 can be inserted more smoothly into the prismatic outer can12.

Next, as shown in FIG. 3A, the flattened wound electrode assembly 11,with the positive electrode collector members 16 and the positiveelectrode intermediate member 24 holding the positive electrodeconnecting conductive members 24A disposed therein, is disposed betweenpairs of resistance welding electrode rods 31 and 32 above and below,and the pairs of resistance welding electrode rods 31 and 32 are eachbrought into contact with one of the positive electrode collectormembers 16, which are disposed on the outermost two surfaces of thepositive electrode substrate exposed portions 14. Then an appropriatedegree of pressure is applied between the pairs of resistance weldingelectrode rods 31 and 32, and resistance welding is performed underparticular predetermined conditions.

In this resistance welding, the positive electrode intermediate member24 is disposed in a stably positioned state between the two split groupsof positive electrode substrate exposed portions 14, and so it ispossible, using just one set of pairs of resistance welding electroderods 31 and 32, to resistance-weld a plurality of positive electrodeconnecting conductive member 24A portions one by one, or, using multiplesets of pairs of resistance welding electrode rods 31 and 32, toresistance-weld a plurality of positive electrode connecting conductivemember 24A portions two or more at a time. With this positive electrodeintermediate member 24 being used in the First Embodiment, thedimensional precision between the connecting conductive members 24A andthe electrode rods 31 and 32 is enhanced, which means that theresistance welding can be done in an accurate and stable state, andvariation in the welding strength will be curbed.

Also, in the positive electrode intermediate member 24 of the FirstEmbodiment, around the positive electrode connecting conductive member24A, the ring-form voids 24 r of the invention are formed between thering-form slots 24 q formed in the resin material portion 24 p of thepositive electrode intermediate member 24, on the one hand, and thesurfaces 24 e and 24 h and the protrusion 24 b of the positive electrodeconnecting conductive member 24A, on the other. Consequently, as shownin FIG. 3B, the spattered dust and melted metal M that occur duringresistance welding will immediately be captured inside the ring-formvoids 24 r formed around the positive electrode connecting conductivemember 24A, and if they collide with the resin material portion 24 p ofthe positive electrode intermediate member 24, will be cooled andcaptured on the surfaces or in the interior of the resin materialportion 24 p, and therefore will seldom leap out to the exterior of thecollector or be dispersed into the interior of the electrode assembly.Thus, as the prismatic sealed secondary battery of the First Embodiment,the prismatic nonaqueous electrolyte secondary battery 10 can beobtained that has low occurrence of internal short-circuits caused bythe spattered dust and melted metal M that occur during resistancewelding, and has stable quality of welds as well as high reliabilitywith improved manufacturing yield.

Note that because an aperture 24 c is formed in the protrusion 24 b ofthe positive electrode connecting conductive members 24A in the FirstEmbodiment, the current will readily concentrate at the tip of theprotrusion 24 b and furthermore the tip of the protrusion 24 b willreadily bite into the positive electrode substrate exposed portions 14.Thus, the weldability is improved over the case where no aperture 24 cis formed. Moreover, the resistance welding is carried out with thepressure being applied so that the tip of the protrusion 24 b issemi-crushed and the portion of the protrusion 24 b that contacts withthe positive electrode substrate exposed portions 14 changes fromannular to circular, then it will be possible to perform the weldingmore stably.

Thus, it is preferable that; for example as shown in FIG. 4D, the shapeof the protrusion 24 b of the positive electrode connecting conductivemembers 24A be made such that the tip of the protrusion 24 b issemi-crushed and the portion of the protrusion 24 b that contacts withthe positive electrode substrate exposed portions 14 changes fromannular to circular. In such a case, a hollow 24 d will be formed in theinterior of the protrusion 24 b. This will make the portion of theprotrusion 24 b that contacts with the positive electrode substrateexposed portions 14 into a circular shape, thereby promoting theemission of heat from the center of the positive electrode connectingconductive member 24A, enabling further stabilized welding.

Note that whether the portion of the protrusion 24 b that contacts withthe positive electrode substrate exposed portions 14 is semi-crushed oris annular is known to depend mainly on the pressure applied duringwelding. The tendency is for the protrusion tip to be annular when thewelding applied pressure is weak, and to be semi-crushed when thewelding applied pressure is strong. Besides that, it is considered thatthe larger the height of the protrusion 24 b and the larger the depth ofthe aperture 24 c, the more readily will the portion be semi-crushed;when the aperture's depth is small, the tip of the protrusion 24 b willmore readily retain its annular shape and be in a condition to bite intothe substrate exposed portions.

During the resistance welding, it is preferable that the central axes ofthe pairs of resistance welding electrode rods 31 and 32 coincide withthose of the positive electrode connecting conductive members 24A, andthat the positive electrode connecting conductive members 24A be held insuch a manner that they will not come out of position due to thepressure application, etc. In addition, a semiconductor type weldingpower source using commonly-known transistors or the like can be used asthe resistance welding machine.

There follows an explanation, using FIGS. 4A to 4D, of the reasons forthe difference arising in the heat-up conditions when the portion of theprotrusion 24 b that contacts with the positive electrode substrateexposed portions 14 is annular and when it is circular. FIG. 4A is aview showing the route by which the resistance welding current flows inthe case where the portion of the protrusion 24 b that contacts with thepositive electrode substrate exposed portions 14 is annular, FIG. 4B isa view showing the portions in FIG. 4A where heat-up is intense, FIG. 4Cis a view showing the route by which the resistance welding currentflows in the case where the portion of the protrusion 24 b that contactswith the positive electrode substrate exposed portions 14 is circular,and FIG. 4D is a view showing the portions in FIG. 4C where heat-up isintense.

Since the current flows through the places with smallest resistance, theportion of the interior of the resistance welding electrode rods 31 and32 where the current flows the most is its center. In the case where theportion of the protrusion 24 b that contacts with the positive electrodesubstrate exposed portions 14 is annular, the welding current I will,for example, flow from the upper resistance welding electrode rod 31through the upper positive electrode collector member 16 and positiveelectrode substrate exposed portions 14 into the annular tip of theupper protrusion 24 b of the positive electrode connecting conductivemember 24A, where the current is split up into an annular stream, whichflows through the interior of the main body 24 a of the positiveelectrode connecting conductive member 24A and into the annular tip ofthe lower protrusion 24 b of the positive electrode connectingconductive member 24A, where the current is focused, and then flowsthough the lower positive electrode substrate exposed portions 14 andpositive electrode collector member 16 into the lower resistance weldingelectrode rod 32, as shown in FIG. 4A. Therefore, in the case where theportion of the protrusions 24 b that contacts with the positiveelectrode substrate exposed portions 14 is annular, the current will notflow in the center of the protrusions 24 b, and as a result, the weldingstart points will occur in an annular configuration, and there will bemultiple start points as shown in FIG. 4B.

By contrast, in the case where the portion of the protrusions 24 b thatcontacts with the positive electrode substrate exposed portions 14 hasbeen semi-crushed and become circular, a hollow 24 d will be formed inthe interior of the protrusion 24 b, and as a result, the weldingcurrent I will, for example, flow from the upper resistance weldingelectrode rod 31 through the upper positive electrode collector member16 and positive electrode substrate exposed portions 14 and into thecenter of the circular tip of the upper protrusion 24 b of the positiveelectrode connecting conductive member 24A, where the current is splitup into an annular stream, which flows through the interior of the mainbody 24 a of the positive electrode connecting conductive member 24A andinto the center of the circular tip of the lower protrusion 24 b of thepositive electrode connecting conductive member 24A, where the currentis focused, and then flows though the lower positive electrode substrateexposed portions 14 and positive electrode collector member 16 into thelower resistance welding electrode rod 32, as shown in FIG. 4C.

In this example, at the protrusion 24 b portion the welding current Iavoids the hollow 24 d and is split up into an annular stream, but sincethe hollow 24 d is present in the central interior of the circular tip,the heat absorption that accompanies the melting of metal is lessened,and so the area around the center of the circular tip of the protrusion24 b becomes the place that heats up most readily. Therefore, in thecase where the portion of the protrusions 24 b that contacts with thepositive electrode substrate exposed portions 14 is circular, thecurrent will be focused in the center of the circular tip of theprotrusion 24 b, and so the shape of the portion that heats up intenselydue to the welding current I will be spherical, as shown in FIG. 4D,which means that the welded state will be more stable and moreover thewelding strength will be high.

Note that the foregoing First Embodiment describes an example in whichthe positive electrode connecting conductive members 24A have a columnarmain body 24 a and truncated cone-shaped protrusions 24 b in whichapertures 24 c are formed. However, with the invention it is possible touse protrusions 24 b in which no apertures are formed, or that aretruncated pyramid-shaped, more precisely, truncated triangular orquadrangular truncated pyramid-shaped, or even multiangular truncatedpyramid-shaped.

In the case where no apertures are formed in the protrusions 24 b, theeffect of the protrusions 24 b will be similar to that of the long-usedprojections during resistance welding. Even in this case, however, itwill be possible to carry out resistance welding satisfactorily betweenthe positive electrode collector member 16, the stacked plurality ofpositive electrode substrate exposed portions 14 and the positiveelectrode connecting conductive members 24A. Where the depth of theapertures 24 c formed in the protrusions 24 b is small, the effectsarising during resistance welding will gradually approach those when noapertures are formed in the protrusions 24 b.

Although an example has been described in which items having a circularcolumnar main body 24 a were used as the positive electrode connectingconductive members 24A, any item having the form of a metallic block,such as square cylindrical, elliptical cylindrical, or the like shape,will be suitable, and it will further be possible to use an item inwhich the aperture 24 c (see FIGS. 2A to 2G) penetrates fully throughthe main body 24 a. Particularly in the case where the aperture 24 cpenetrates fully through the main body 24 a, the main body 24 a of thepositive electrode connecting conductive members 24A will becylindrical, but in such a case the main body 24 a can be made to alsoserve as protrusions by forming the two ends thereof or leaving themprojecting. In such a case where the main body 24 a of the positiveelectrode connecting conductive members 24A is cylindrical, it will beadvisable to make the cylindrical portion thicker to a certain degree,in order to render the electrical resistance small.

The foregoing First Embodiment describes the case where the stackedplurality of positive electrode substrate exposed portions 14 are splitinto two groups and resistance welding is performed using the positiveelectrode collector members 16 and the positive electrode connectingconductive members 24A, but alternatively the positive electrodeconnecting conductive members 24A could be made to also serve aspositive electrode collector members, and be connected to the positiveelectrode terminal 17. In such a case it will suffice to employ, inplace of the positive electrode collector members used in the FirstEmbodiment, a welding receiving member constituted of thin sheetmaterial formed from the same material as the positive electrodeconnecting conductive members 24A.

Second to Fourth Embodiments

The First Embodiment describes, for the positive electrode connectingconductive members 24A that are held by the positive electrodeintermediate member 24, an item in which a protrusion 24 b that is,e.g., truncated pyramid-shaped, is formed on each of two opposed faces24 e of the circular columnar main body 24 a, as shown in FIGS. 2B and2C. Thus, when the main body 24 a is circular columnar, angled portions24 f will be formed between the two opposed faces 24 e and side faces 24h of the circular columnar main body 24 a. Therefore, as shown in FIGS.3A and 3B, when the positive electrode intermediate member 24 holdingthe positive electrode connecting conductive members 24A is disposedinside the two split groups of stacked positive electrode substrateexposed portions 14, so that each of the truncated pyramid-shapedprotrusions 24 b on the two ends of the positive electrode connectingconductive members 24A contacts against the stacked positive electrodesubstrate exposed portions 14, then if the angled portions 24 f protrudeexposed from the surface of the positive electrode intermediate member24, the exposed angled portions 24 f will more readily contact with thestacked positive electrode substrate exposed portions 14, and thepositive electrode substrate exposed portions 14 will readily deform.

Accordingly, for the positive electrode connecting conductive member 24Bof a Second Embodiment of the invention, surfaces 24 g provided withchamfered portions are formed on the angled portions 24 f between thetwo opposed faces 24 e and side faces 24 h of the circular columnar mainbody 24 a of the First Embodiment. This positive electrode connectingconductive member 24B of the Second Embodiment will now be describedusing FIG. 5A. Note that FIG. 5A is a front view of a positive electrodeconnecting conductive member 24B of the Second Embodiment.

With the positive electrode connecting conductive member 24B of theSecond Embodiment, which has surfaces 24 g provided with chamferedportions as mentioned above, even if the surfaces 24 g provided withchamfered portions protrude from the surface of the positive electrodeintermediate member 24, when the positive electrode intermediate member24 holding the positive electrode connecting conductive members 24B isdisposed inside the two split groups of stacked positive electrodesubstrate exposed portions 14, so that each of the truncated cone-shapedprotrusions 24 b on the two ends of the positive electrode connectingconductive members 24B contacts against the stacked positive electrodesubstrate exposed portions 14, little damage will be caused to thestacked positive electrode substrate exposed portions 14, and insertionas far as the position for welding to the positive electrode substrateexposed portions 14 will be easy. Hence, the weldability will beimproved.

Either curved surfaces or planes can be employed for the surfaces 24 gprovided with chamfered portions of the positive electrode connectingconductive members 24B of the Second Embodiment. However, if thesurfaces 24 g provided with chamfered portions are made into planes,then the surfaces 24 g provided with chamfered portions and the surfaceson which the protrusion 24 b is formed will, of necessity, form obtuseangles with respect to the positive electrode substrate exposed portions14, and so the positive electrode substrate exposed portions 14 and theprotrusions 24 b will readily come into contact when the positiveelectrode connecting conductive members 24B is brought into contact withthe stacked positive electrode substrate exposed portions 14, with theresult that the weldability will be improved.

As regards the positive electrode connecting conductive members 24C of aThird Embodiment of the invention, as shown in FIG. 5B, these positiveelectrode connecting conductive members 24C exhibit a form such that thesurfaces 24 g provided with chamfered portions are extended as far asthe portion where the protrusion 24 b is formed, and the faces 24 econstituted of the two mutually parallel planar faces on the main body24 a of the positive electrode connecting conductive members 24B of theSecond Embodiment are absent. These positive electrode connectingconductive members 24C of the Third Embodiment will also yield fairlygood resistance welding advantages.

However, the configuration with the two faces 24 e where the protrusion24 b is provided both being exposed, as in the positive electrodeconnecting conductive members 24B of the Second Embodiment is used, moreprecisely, the configuration whereby two mutually parallel planar facesare formed on the main body 24 a of the positive electrode connectingconductive members 24B, is more preferable, because when the pressure isapplied to the resistance welding electrode during resistance welding,the positive electrode connecting conductive members 24B will not beprone to deform, and part of the protrusion 24 b that melts and deforms,or part of the positive electrode substrate exposed portions 14 thatmelt, during resistance welding, will dwell on these surfaces 24 e andbe inhibited from flowing out toward the sides of the positive electrodeconnecting conductive members 24B, and moreover, since the faces 24 ewill be the faces that contact with the positive electrode substrateexposed portions 14, the positions of the positive electrode connectingconductive members 24B will be stabilized, and it will be possible toobtain higher-reliability resistance welds.

Furthermore, the positive electrode connecting conductive members 24D ofa Fourth Embodiment of the invention are the positive electrodeconnecting conductive members 24B of the Second Embodiment, butprovided, in the central portion of the protrusions 24 b, with apertures24 c having a depth D that is smaller than the height H of theprotrusions 24 b.

FIG. 5D is a schematic side view that illustrates resistance weldingcarried out using the positive electrode connecting conductive members24D of the Fourth Embodiment in order to show that when the surfaces 24g provided with chamfered portions are formed, as in the positiveelectrode connecting conductive members 24B to 24D of the Second toFourth Embodiments, the positive electrode intermediate member 24 canmore readily be inserted between the two split groups of positiveelectrode substrate exposed portions 14. It will be seen from FIG. 5Dthat even with the positive electrode connecting conductive members 24Dprotruding from the surface of the positive electrode intermediatemember 24, the positive electrode substrate exposed portions 14 will notbe prone to deform geometrically. FIG. 5D also illustrates the casewhere the angled portions on the side of the positive electrodeintermediate member 24 that is inserted between the positive electrodesubstrate exposed portions 14 are chamfered. It will also be seen fromFIG. 5D that due to the shape of the positive electrode intermediatemember 24, the positive electrode substrate exposed portions 14 will notbe prone to deform geometrically even when the positive electrodeintermediate member 24 is inserted between the two split groups ofpositive electrode substrate exposed portions 14.

Fifth and Sixth Embodiments

In the First to Fourth Embodiments above, examples are described inwhich the positive electrode substrate exposed portions 14 of theflattened wound electrode assembly 11 are split into two groups, one oneach side relative to the winding center portion, each such group isbundled together, positive electrode collector members 16 are placedagainst the two outermost surfaces of the positive electrode substrateexposed portions 14, a positive electrode intermediate member 24 havingpositive electrode connecting conductive members 24A, 24B, 24C or 24D isinserted between the two split groups of positive electrode substrateexposed portions 14, and resistance welding is performed by bringingpairs of resistance welding electrodes 31, 32 into contact with bothsurfaces of the positive electrode collector members 16 (see FIGS. 3Aand 3B). However, with the present invention, it is not necessarily anecessary condition to place positive electrode collector members 16connected to the positive electrode terminal 17 against both of theoutermost surfaces of the two split groups of positive electrodesubstrate exposed portions 14; it will suffice to perform resistancewelding with positive electrode collector members 16 placed against atleast one surface of the two split groups of positive electrodesubstrate exposed portions 14.

There follows a description, using FIGS. 6A and 6B, of the post-weldingdisposition of the positive electrode connecting conductive member 24portion in Fifth and Sixth Embodiments of the invention, in which, asmentioned above, positive electrode collector members 16 connected tothe positive electrode terminal 17 are placed against at least onesurface of the two split groups of positive electrode substrate exposedportions 14. Note that FIG. 6A is a side view showing the post-weldingdisposition of the positive electrode connecting conductive member 24portion in the Fifth Embodiment, and FIG. 6B is a side view showing thepost-welding disposition of the positive electrode connecting conductivemember 24 portion in the Sixth Embodiment. The descriptions of the Fifthand Sixth Embodiments use positive electrode intermediate members 24that have the same positive electrode connecting conductive members 24Aas the items used in the First Embodiment.

In the Fifth Embodiment, as shown in FIG. 6A, a positive electrodecollector member 16 connected to the positive electrode terminal 17 isdisposed so as to contact against one outermost surface of the two splitgroups of positive electrode substrate exposed portions 14, a positiveelectrode collection receiving member 16 a is disposed so as to contactagainst the other outermost surface of the two split groups of positiveelectrode substrate exposed portions 14, and resistance welding isperformed by placing pairs of resistance welding electrodes into contactwith the positive electrode collector member 16 and the positiveelectrode collection receiving member 16 a. In this Fifth Embodiment,the positive electrode collection receiving member 16 a is not directlyconnected to the positive electrode terminal 17, but fulfills the roleof receiving one of the pairs of resistance welding electrodes duringresistance welding. Even with a structure such as in the FifthEmbodiment, substantially the same advantageous effects are yielded asin the First Embodiment, because of the projection effect possessed bythe positive electrode connecting conductive members 24A of the positiveelectrode intermediate member 24. More precisely, the collectionreceiving member 16 a yields substantially the same advantageous effectsas the positive electrode collector member 16 with regard to resistancewelding. The meaning of “collector member” as used herein includes sucha “collection receiving member”. Disposing collector members on both theoutermost surfaces of the two split groups of positive electrodesubstrate exposed portions 14 enables resistance welding to be performedin a physically stable state.

In the Sixth Embodiment, as shown in FIG. 6B, a positive electrodecollector member 16 is disposed so as to contact against one outermostsurface of the two split groups of positive electrode substrate exposedportions 14, nothing is provided on the other outermost surface of thetwo split groups of positive electrode substrate exposed portions 14,and resistance welding is performed by placing pairs of resistancewelding electrodes into contact with the positive electrode collectormember 16 and the other outermost surface of the two split groups ofpositive electrode substrate exposed portions 14. More precisely, in theSixth Embodiment, one of the pair of resistance welding electrodes isplaced directly into contact with the other outermost surface of the twosplit groups of positive electrode substrate exposed portions 14 inorder to perform resistance welding. With a configuration such as in theSixth Embodiment, fairly good resistance welding can be performedbecause of the projection effect possessed by the positive electrodeconnecting conductive members 24A of the positive electrode intermediatemember 24, but since there is a possibility of fusion occurring betweenthe resistance welding electrodes and the other outermost surface of thepositive electrode substrate exposed portions 14, it is preferable thata positive electrode collector member 16 or a collection receivingmember 16 a be disposed on the other outermost surface of the positiveelectrode substrate exposed portions 14, as in the First to FifthEmbodiments.

Seventh to Tenth Embodiments

In the First Embodiment, an example is described that used a positiveelectrode intermediate member 24 made of synthetic resin and having arectangular parallelepiped shape. However, since any shape that can holdthe connecting conductive members 24A stably can be used to implementthe invention, the shape of the positive electrode intermediate member24 is not limited to a rectangular parallelepiped. For example, cutoutportions 24 x could be formed in between the positive electrodeconnecting conductive members 24A as in the positive electrodeintermediate member 24 ₁ of a Seventh Embodiment of the invention shownin FIG. 7A, or through holes 24 y could be formed longitudinally as inthe positive electrode intermediate member 24 ₂ of an Eighth Embodimentof the invention shown in FIG. 7B, or apertures 24 z could be formed inbetween the positive electrode connecting conductive members 24A as inthe positive electrode intermediate member 24 ₃ of a Ninth Embodiment ofthe invention shown in FIG. 7C. If such structures are employed, thecutout portions 24 x, through holes 24 y, apertures 24 z, or the likewill act as gas venting routes, so that any gas that may be generated inthe electrode assembly interior if abnormality occurs in the battery caneasily be expelled to the exterior of the electrode assembly, and sincethe pressure-sensitive type current interruption mechanism, gas exhaustvalve, and so forth, with which a prismatic sealed secondary battery isnormally equipped will be activated stably, safety can be secured, and ahigh-reliability prismatic sealed secondary battery can be manufactured.

Tenth to Twelfth Embodiments

A positive electrode intermediate member 24 ₄ of a Tenth Embodiment ofthe invention, a positive electrode intermediate member 24 ₅ of anEleventh Embodiment, and a positive electrode intermediate member 24 ₆of a Twelfth Embodiment, will now be described using FIGS. 8A, 8B and8C, respectively. Note that FIG. 8A is a longitudinal sectional view ofthe positive electrode intermediate member 24 ₄ pertaining to the TenthEmbodiment, FIG. 8B is a longitudinal sectional view of the positiveelectrode intermediate member 24 ₅ pertaining to the EleventhEmbodiment, and FIG. 8C is a longitudinal sectional view of the positiveelectrode intermediate member 24 ₆ pertaining to the Twelfth Embodiment.FIGS. 8A to 8C all show examples that use positive electrode connectingconductive members 24A of the same shape as those in Embodiment 1.

The positive electrode intermediate member 24 ₄ of the Tenth Embodimentis the positive electrode intermediate member 24 of the First Embodimentshown in FIGS. 1 to 3, but without slots being specially formed in aring-form in the resin material portion 24 p located around the positiveelectrode connecting conductive member 24A; instead, the spaces formedbetween the resin material portion 24 p of the positive electrodeintermediate member 24 ₄, on the one hand, and the surfaces 24 e and theprotrusions 24 b of the positive electrode connecting conductive members24A, on the other hand, are utilized unaltered as ring-form voids 24 r1. With the use of such positive electrode intermediate member 24 ₄ ofthe Tenth Embodiment also; the spattered dust and melted metal thatoccur during resistance welding will be captured inside the ring-formvoids 24 r 1 formed around the positive electrode connecting conductivemember 24A, and if they collide with the resin material portion 24 p ofthe positive electrode intermediate member 24 n, will be cooled andcaptured on the surfaces or in the interior of the resin materialportion 24 p, and therefore will seldom leap out to the exterior of thecollector or be dispersed into the interior of the electrode assembly.

Thus, as the prismatic sealed secondary battery of the Tenth Embodimentalso, a prismatic nonaqueous electrolyte secondary battery can beobtained that has low occurrence of internal short-circuits caused bythe spattered dust and melted metal that occur during resistancewelding, and has stable quality of welds as well as high reliabilitywith improved manufacturing yield.

The positive electrode intermediate member 24 ₅ of the EleventhEmbodiment is the positive electrode intermediate member 24 ₄ of theTenth Embodiment, but additionally with ring-form slots 24 q that areformed, in such a manner as to encircle the positive electrodeconnecting conductive members 24A, in the resin material portion 24 p atpositions distanced from the resistance welding portions, the latterbeing the positions where the protrusions 24 b are formed. Thesering-form slots 24 q may be of any depth and width.

More precisely, the positive electrode intermediate member 24 ₅ of theEleventh Embodiment is equipped with ring-form voids 24 r 1 constitutedof the spaces between the resin material portion 24 p of the positiveelectrode intermediate member 24 ₅, on the one hand, and the surfaces 24e and the protrusions 24 b of the positive electrode connectingconductive members 24A, on the other hand; and with ring-form voids 24 r2 constituted of the ring-form slots 24 q. With the use of such positiveelectrode intermediate member 24 ₅ of the Eleventh Embodiment also, thespattered dust and melted metal that occur during resistance weldingwill, as in the case of the positive electrode intermediate member 24 ₄of the Tenth Embodiment, be captured inside the ring-form voids 24 r 1formed around the positive electrode connecting conductive member 24A,and if they collide with the resin material portion 24 p of the positiveelectrode intermediate member 24 ₅, will be cooled and captured on thesurfaces or in the interior of the resin material portion 24 p.

In addition, the spattered dust and melted metal occurring duringresistance welding that are not captured in the aforementioned partswill migrate toward points further distanced from the welds, and whilethey do so their temperature will fall, as will their speed also, sothat they will readily be captured inside the ring-form voids 24 r 2constituted of the ring-form slots 24 q. Thus, in the case where thepositive electrode intermediate member 24 ₅ of the Eleventh Embodimentis used, it will even more seldom occur than in the case where thepositive electrode intermediate member 24 ₄ of the Tenth Embodiment isused, that the spattered dust and melted metal that occur duringresistance welding will leap out to the exterior of the collector or bedispersed into the interior of the electrode assembly.

Thus, as the prismatic sealed secondary battery of the EleventhEmbodiment, a prismatic nonaqueous electrolyte secondary battery can beobtained that has even lower occurrence of internal short-circuitscaused by the spattered dust and melted metal that occur duringresistance welding, and has even stabler quality of welds as well ashigher reliability with improved manufacturing yield, than the prismaticnonaqueous electrolyte secondary battery of the Tenth Embodiment.

The positive electrode intermediate member 24 ₆ of the TwelfthEmbodiment is equipped with only the ring-form voids 24 r 2 constitutedof the ring-form slots 24 q formed in the resin material portion 24 p ofthe positive electrode intermediate member 24 ₆. With the use of suchpositive electrode intermediate member 24 ₆ of the Twelfth Embodimentalso, the spattered dust and melted metal that occur during resistancewelding will, as in the case of the positive electrode intermediatemember 24 ₄ of the Tenth Embodiment, be cooled and captured on thesurfaces or in the interior of the resin material portion 24 p of thepositive electrode intermediate member 24 ₆, and those of them that arenot captured by the resin material portion 24 p will be captured insidethe ring-form voids 24 r 2 formed around the positive electrodeconnecting conductive members 24A. Thus, even where the positiveelectrode intermediate member 24 ₆ of the Twelfth Embodiment is used,the spattered dust and melted metal that occur during resistance weldingwill seldom leap out to the exterior of the collector or be dispersedinto the interior of the electrode assembly.

Note that although the descriptions of the First to Twelfth Embodimentsabove concerned the positive electrode part, the negative electrode partemploys the same structure—except for different physical properties ofthe materials of the negative electrode substrate exposed portions 15,negative electrode collector members 18, negative electrode intermediatemember 25, negative electrode connecting conductive members 25A, andnegative electrode collection receiving member (not shown in thefigures), and therefore, yields substantially the same effects andadvantages. Furthermore, the invention does not necessarily have to beemployed in both the positive electrode part and the negative electrodepart, and may be applied to the positive electrode part alone or to thenegative electrode part alone.

Also, although the foregoing First to Twelfth Embodiments describeexamples in which the slots formed in the resin material portion of theintermediate member are “ring-form”, the fact that with the invention,the spattered dust and melted metal that occur during resistance weldingare also captured by the resin material portion of the intermediatemember means that the slots do not necessarily need to be formed asperfect rings; they may be formed discontinuously (with gapped portionsin the ring) around the resistance-welded portions of the connectingconductive members, and as regards their shape, they may take the formof a circular ring, an elliptical ring, or even a rectangular ring—anydesired shape may be employed for them. Furthermore, although theforegoing First to Twelfth Embodiments describe examples in which thecross-sectional form of the slots is flat-bottomed, it couldalternatively be round-bottomed or V-shaped.

In the manufacture of a prismatic sealed secondary battery of theinvention it is possible to use positive electrode connecting conductivemembers and negative electrode connecting conductive members withprotrusions of differing shapes. Differing metallic materials are usedfor the positive electrode substrates and the negative electrodesubstrates of an ordinary sealed battery. For example, in a lithium ionsecondary battery, aluminum or aluminum alloy is used for the positiveelectrode substrates and copper or copper alloy is used for the negativeelectrode substrates. Because copper and copper alloy have lowelectrical resistance compared with aluminum and aluminum alloy, it ismore difficult to resistance-weld the negative electrode substrateexposed portions than to resistance-weld the positive electrodesubstrate exposed portions, and hard-to-melt portions are prone to occurin the stacked negative electrode substrate exposed portion interior.

In such a case, it will be desirable, in order to concentrate theelectric current and render the resistance welding easy to perform, touse protrusions with apertures formed therein for the shape of theprotrusions of the negative electrode connecting conductive members thatare used between the negative electrode substrate exposed portions,while for the shape of the protrusions of the positive electrodeconnecting conductive members that are used between the positiveelectrode substrate exposed portions, it will be desirable to useprotrusions without apertures formed therein, so that the resistancewelding will proceed easily and the positive electrode connectingconductive members will be less liable to deform.

The foregoing embodiments and figures set forth examples in which, forsimplicity of description, welding is carried out using one intermediatemember, which holds two connecting conductive members, for the substrateexposed portions of each electrode. However, the number of connectingconductive members can of course be one or three or more, and can bedetermined appropriately in accordance with the size, required output,and other characteristics of the battery.

What is claimed is:
 1. A prismatic sealed secondary battery comprising:an electrode assembly that has stacked or wound positive electrodesubstrate exposed portions and negative electrode substrate exposedportions; a positive electrode collector member that is electricallyjoined to the positive electrode substrate exposed portions; a negativeelectrode collector member that is electrically joined to the negativeelectrode substrate exposed portions; and a prismatic outer can, thepositive electrode substrate exposed portions or the negative electrodesubstrate exposed portions, or both, being split into two groups, andtherebetween being disposed an intermediate member that is made of aresin material and holds one or more connecting conductive members, thecollector member for the substrate exposed portions that are split intotwo groups being disposed on at least one of the outermost faces of thesubstrate exposed portions that are split into two groups, and beingelectrically joined by a resistance welding method to the substrateexposed portions that are split into two groups, together with the oneor more connecting conductive members, and voids being formed in theresin material portions of the intermediate member that are locatedaround the resistance-welded portions of the connecting conductivemembers.
 2. The prismatic sealed secondary battery according to claim 1,wherein the voids are constituted of slots formed between the resinmaterial portions of the intermediate member and the connectingconductive members.
 3. The prismatic sealed secondary battery accordingto claim 1, wherein the voids are constituted of slots formed in theresin material portions in positions distanced from theresistance-welded portions.
 4. The prismatic sealed secondary batteryaccording to claim 1, wherein the electrode assembly is inserted intothe prismatic outer can in such a manner that the positive electrodesubstrate exposed portions are positioned at one end, and the negativeelectrode substrate exposed portions at the other end, of the prismaticouter can, and thus that the resin material portions of the intermediatemember protrude, in the extension direction of the two split groups ofsubstrate exposed portions, beyond the ends of the two split substrateexposed portions and the ends of the collector member to the prismaticouter can.
 5. The prismatic sealed secondary battery according to claim4, wherein flat portions are provided on portions of the resin materialportions of the intermediate member that are opposed to the prismaticouter can.
 6. The prismatic sealed secondary battery according to claim5, wherein chamfered portions are formed on the angled portions of theresin material portions of the intermediate member that are opposed tothe prismatic outer can.
 7. The prismatic sealed secondary batteryaccording to claim 1, wherein chamfered portions are formed on theangled portions of the resin material portions of the intermediatemember that are on the side that is inserted into the substrate exposedportions that are split into two groups.
 8. The prismatic sealedsecondary battery according to claim 1, wherein the resin materialportions of the intermediate member are provided with a gas venting holeor cutout, or both.
 9. The prismatic sealed secondary battery accordingto claim 8, wherein the connecting conductive members are block-shapedor columnar body-shaped.
 10. The prismatic sealed secondary batteryaccording to claim 9, wherein the angled portions of two mutuallyopposed surfaces of the block shapes or columnar body shapes of theconnecting conductive members have chamfered portions.
 11. The prismaticsealed secondary battery according to claim 10, wherein the surfacesprovided with the chamfered portions of the connecting conductivemembers are planes.